The function of the crown adjustment on a cold rolling strip mill is to shape the profile of the roll gap to the profile of the strip entering the mill, in order to produce uniform elongation, and hence good flatness of the strip being processed.
The crown adjustment mechanism on all Sendzimir large cluster mills since 1957 has been effected via an eccentric ring mounted in each respective support saddle in the uppermost two backing shafts. The eccentric ring has two gear pinions mounted to it, one on each side, and attached to the ring by rivets. A rack engages with the gear pinions and causes rotation of the eccentric ring as it is traversed. An independent drive is supplied for each rack, so that the position of the backing shaft can be adjusted at each saddle location. A typical construction of the adjustment mechanism of rack, pinions and eccentric rings is shown in FIG. 9 of U.S. Pat. No. 3,147,648. It is also shown in FIGS. 3-6 of U.S. Pat. No. 4,289,013.
The method of driving the adjustment mechanism at each saddle is a matter of design choice In most cases it has been done by a screw jack driven by a hydraulic motor (type 1); in some cases by a screw jack driven by an electric motor (type 2); and in some cases by a hydraulic cylinder (type 3). U.S. Pat. No. 3,478,559 disclosed the use of hydraulic cylinders for crown adjustment in 1969.
During the years since 1957 various methods of indicating the position of the adjustment mechanisms have been used. The earliest systems used simple mechanical pointers directly mounted on the drive mechanism on top of the mill, which were difficult to read. Subsequently, beginning in the 1960's, selsyn indicators with circular dials were used, but did not give the operator a graphic "picture" of the profile set by the various drives Starting in the late 1960's efforts were made to give the operator a better "picture" by arranging the indicators vertically side by side so that relative positions of the adjustment mechanisms, and hence the shape of the mill profile could be seen at a glance. The earliest systems of this kind, mostly installed in Japan, used a system of pulleys and cables so that the movement of a particular crown adjustment rack was directly coupled to the corresponding pointer on the scale, producing proportional concomitant movements of the pointer.
Beginning in the early 1970's, position transducers, such as potentiometers or differential transformers (LVDT's or RVDT's), were used to sense rack position, and were electrically connected to edge type moving coil meters mounted vertically side by side in the operator's desk, as remote readouts of rack position. By the mid 1970's, linear bar graph indicators, consisting of rows of light emitting diode elements, such as those made by Dixson, Inc., of Grand Junction, Colo., became available, and were used in place of the moving coil meters. Such position indication systems are quite common today.
U.S. Pat. No. 4,022,040, which is incorporated herein by reference, teaches how to couple all the crown adjustment drives (type 1 or type 2) together mechanically, using a system of gears and differentials, to achieve the ability to operate all drives together in a synchronized mode, while retaining the ability to operate them individually. The relationship between motions of the various drives is determined by the gear ratios, and can be either set to give "taper" (also known as "tilt") adjustment, or to give "crown" adjustment in response to a single pushbutton command by the operator (but not both).
U.S. Pat. No. 4,156,359 teaches how "tilt" and "crown" adjustment of the drives in response to a single push button command could both be achieved, but without the ability to operate the drives individually. The crown adjustment is controlled by the rotation of a shaft having eccentric cams, carried by a frame pivotably mounted above the roll. Tilting of the frame produces a concurrent tilt of the crown shape.
Thus, there is a need in the art for a mill control system which allows both the crown and tilt to be adjusted, while retaining the ability to adjust the saddles individually. Individual saddle adjustment which allows the position at each saddle to be varied in order to accommodate tolerances or other deviations is also needed. Such a mill control system should preferably be responsive to single key stroke or push button commands in order to allow easy operation.